1. Field of the Invention
The present invention relates to an apparatus and a method for detecting and delineating cancerous lesions, and more particularly an apparatus and a method for effective and affordable early detection of cancerous lesions using gamma rays or other radiation to obtain image data. In addition, the present invention relates to applying contrast material to a medical device for the purpose of making it visible to imaging equipment and specifically to applying a radioactive contrast material to a medical device used for tissue marking, sampling, excision or therapy for the purpose of making it visible to nuclear-emission imaging equipment.
2. Description of the Related Art
Cancer is a major threat and concern to the population. Early detection and complete treatment of suspicious or cancerous lesions has been shown to improve long-term survival. Medical imaging modalities such as magnetic resonance imaging (MRI), x-ray, and ultrasound are often deployed to detect small, non-palpable lesions. Once detected, a tissue sample, or biopsy, from the lesion is obtained using position information from one or more of these medical imaging modalities. The tissue sample is then analyzed for the presence of cancer to determine if the lesion requires treatment. If the lesion is found to require treatment (e.g., excision, ablation, or radiation), position information from a medical imaging modality is sometimes used to localize the borders of the lesion so that not more nor less tissue than necessary is treated.
There are a myriad of devices to mark, sample (i.e., biopsy), and treat (e.g., excision, ablation, radiate, or poison) suspicious or cancerous tissue using image localization. Each of these devices produces a signal that can be detected by one or more medical imaging modalities. This signal can be used to ensure the device has been positioned properly in relation to the suspect tissue.
One example of a marking device and method is the common wire-localized biopsy, where an x-ray-opaque guide wire is used to localize non-palpable lesions detected by x-ray or ultrasound for subsequent biopsy or excision. A hollow needle with an open, sharpened tip is inserted percutaneously, into or near the suspect tissue, based on x-ray or ultrasound positioning. The guide wire, typically having a spring-loaded anchoring hook at its tip, is then introduced through the needle and advanced until the anchoring tip projects out the distal end of the needle, at which point the hook is deployed, thus resisting backward displacement of the wire. The needle is then withdrawn, leaving the guide wire in the desired position. The final position of the wire with respect to the lesion is determined and confirmed with subsequent x-ray or ultrasound views. The guide wire is then used in surgery as a physical representation of the position of the lesion to guide a biopsy or excision. It is critical that the position of the guide wire(s) accurately depict the position of the lesion in order to ensure that a proper tissue sample is obtained for analysis, or to ensure that the borders of the lesion are accurately represented for a complete excision of the lesion with minimal complications, scarring and deformity.
Another example of a sampling or biopsy device and method used to localize non-palpable lesions detected by imaging is the common image-guided core-biopsy needle procedure. The core biopsy needle is a minimally-invasive tissue sampling device that can be introduced percutaneously into suspect tissue based on x-ray, ultrasound, or MRI positioning. The needle has an aperture or sampling window for capturing and removing tissue after its position in relation to the lesion has been established by x-ray, ultrasound, or MRI imaging. It is critical that the position of the sampling window is within or directly adjacent to the suspect tissue, in order to ensure that a proper sample is obtained for analysis.
In U.S. Pat. Nos. 6,840,948 and 6,855,140, the contents of both of which are incorporated herein by reference, Albrecht, et al. disclose an example of a method and device to treat cancerous lesions by excision. The disclosures of those two patents describe a means for the intact removal of a lesion under image guidance. A rotatable electrode is inserted into the tissue and positioned adjacent to the lesion, such that by rotationally driving the electrode, it envelops the lesion, thus severing it from the surrounding tissue for intact removal. Imaging is used to assist in placement of the probe, and to assess a desired excision volume. To ensure a complete removal of the cancerous tissue using this method, it is critical to position the electrode directly adjacent to the lesion and confirm the placement with imaging before the excision.
The effectiveness of each of these methods relies on the accuracy of image localization, including x-ray, ultrasound, and potentially MRI, to delineate suspect tissue and to describe the position of the device in relation to that delineation. Thus, the success of the localization and the ensuing procedures relying on that localization are strongly related to the accuracy of the imaging modality.
Nuclear medicine techniques have been adapted for measuring biochemical functions in the human body. One of these methods, known as positron emission tomography (PET), is the detection of gamma rays emitted from tissues after administration of a substance, such as glucose or fatty acids, into which positron emitting isotopes (radiotracers) have been incorporated. A computer algorithm interprets the paths of the gamma rays that result from collisions of positrons and electrons, and the resultant tomogram represents the distribution of the isotope within the imaged tissue.
PET produces images of the body's basic biochemistry or function. Traditional diagnostic techniques, such as x-rays, x-ray computed tomography (CT) scans, or MRI, produce images of the body's anatomy or structure. These techniques can detect diseases when changes in structure or anatomy that occur with disease can be seen.
Biochemical processes are also altered with disease and may occur before there is a detectable change in gross anatomy. PET is an imaging technique that is used to visualize some of these processes that change. PET is a very useful addition to the clinician's diagnostic toolbox, providing significant advances to traditional diagnostic methods.
In cancer imaging, PET that uses the administration of the radiotracer fluorodeoxyglucose (i.e., FDG-PET) is a method of measuring the rate of glucose metabolism within tissue. Increased glucose metabolism is often associated with neoplastic processes. FDG-PET is becoming standard in clinical diagnostic practice, as increased glucose metabolism is one of the earliest methods of cancer detection.
Prior versions of flexible devices for imaging body parts under immobilization and/or compression have employed one detector head above and one detector head below the body part. These configurations allow high spatial resolution to be achieved by minimizing distance between the detector heads and the source of radiation, thereby reducing non-collinearity error, and similarly provide high count sensitivity, due to the fact that radiation detection sensitivity per unit detector area increases as the square of the distance from the source decreases.
Prior versions of flexible devices have featured moving detector heads which conserve component cost and increase access by the user to the body part. Component cost is reduced, since the geometry of acquisition is so sensitive to radiation emitted by the source that it is not necessary to cover the entire face of the body part with detector material. Increased access is achieved by having the detector move out of the way once it has collected enough information to form a high-confidence image. A window is featured that allows a user to mark the body part or perform an interventional or diagnostic procedure once the detector head is out of the way.
Volumetric acquisition of lines of response is obtained with the detector heads, since lines of response impinging one edge of one detector head cross the body part to impinge on the opposite edge of the other detector head. The plurality of such diagonal and/or oblique lines of response passing through a region of tissue provides information as to the depth and strength of sources in the body part under investigation.
As described above, the accuracy of orienting a device in proper relation to the suspect tissue is critical to the success of the ensuing procedure. Thus, in order to perform an effective intervention, such as a biopsy, it is helpful to see both the target (e.g., a suspected tumor) and the interventional device (e.g., a biopsy needle, cannula). Because most interventional devices do not emit radioactivity, they are not visible on PET images. Therefore, it is desirable to find a method of simultaneously imaging the interventional devices and the areas of abnormal tissue with the PET scanner.
U.S. Pat. No. 5,647,374, the contents of which are incorporated herein by reference, describes a stylus comprising a tube having radioactive material in the tip capable of being imaged, the stylus contained within a needle. An image of the tip of the needle can then be traced using gamma ray (also known as nuclear-emission) imaging as the needle penetrates a human body. The position of the radioactive tip of the stylus can be assessed as it approaches a region of suspect tissue, in order to achieve accurate placement within the lesion. Then, the stylus is removed and a guide wire is advanced through the needle. One shortcoming of this method is that once the stylus is removed, it is no longer possible to verify the location, in relation to the suspect tissue, of the guide wire or of any subsequently positioned device. Another shortcoming of this method is that the radioactive stylus device contains only a point source of radioactivity. Thus, the location of the axis of the stylus in relation to the suspect tissue could not be verified with nuclear-emission imaging. This would be a disadvantage in procedures in which more than one visible point is needed. More than one visible point would likely be needed, for example, to demonstrate an orientation of the stylus. Other situations may exist for which a single radioactive point would not be as effective as multiple radioactive points or lines. For example, it would be useful to have more than one radioactive point on the stylus in order to demonstrate the relative extent of a lesion with respect to the radioactive stylus. This would be useful in a lesion bracketing procedure (see, e.g., Silverstein, Ductal Carcinoma In Situ of the Breast; 1997, the contents of which are incorporated herein by reference), in which the perimeter of the lesion is demarcated by multiple wires that define all of its perimeter, depth and position. Additionally, if there is only one radioactive point on the stylus, that point might not be visible on the PET image once the radioactive point enters the abnormal region of tissue. Thus, having multiple radioactive points could provide useful redundancy.